There is a Capital Gains exemption for your principle residence.
http://www.cra-arc.gc.ca/E/pub/tg/t4037/t4037-e.html#P298_31900
#1
Since DM sold that home to MB for $1.00 then he would not pay capital gains tax. However, since, IMO it is not MB's principal residence, ( wouldn't her principal residence be in Kleinburg?) then she is responsible for the capital gains tax as she was the owner when it was sold. Her purchase price is $1.00 her sale price is $1.2 million, that is one heck of a capital gain. Plus, 50% of the capital gain gets added to her income that year, and I am sorry I should have said a 50% tax bracket which is then a $300,000 tax bill plus all of her other income is taxed at that same bracket. She then loses all of her age tax credits ( assuming she has them ).
Hopefully this isn't considered sleuthing MB but more so of stating tax implications. When someone is prepared to take on that kind of a tax burden there must be a really good reason for selling that property. ( needing money)
Just my own opinion.
#2
Who knows what is buried beneath the ground but I sure wouldn't want to be the new owner, that is for sure. Again, Just my own opinion